Requiem
by MistyNocturne
Summary: After all these years, Arthur did rise again. But entirely for the wrong reasons. With Excalibur in his hand once more, Merlin sets out one last time to end this madness. Oneshot. Antichrist/Devil!Arthur. Merlin/Damien Crossover.
**Disclaimer: I don't own BBC Merlin nor A &E's Damien. If I did, then the latter would be about Damien being conflicted between being Arthur Pendragon or the Devil's son, and Merlin finally reuniting (happily) with him. *sobs***

 **A/N: I realize no one's actually done a proper Merlin and Damien crossover yet. So I decided to write one myself lolz. It's pretty hard to imagine Bradley as the bad guy in anything really. But heck. The idea of seeing him try it is keeping me hyped at the moment. So far, Damien's moving at a very draggy pace, and I feel as though they can do a** ** _lot_** **more in those 40-minute intervals; the only redemption of the show being Bradley's facial expressions and great angsty moments. Couldn't get this idea out of my system, but due to lack of material and episodes to refer to, it was hard to make it happen. Please forgive my most amateurish writing.**

 **Soundtracks for this fic: Doomsday from Doctor Who, How'm I supposed to Die by Civil Twilight and Assassin's Creed by Zyrah**

 **This is endgame. Don't like, don't read! No flames, please!**

 **~.~.~.~**

From the dawn of time to the end of days, mankind had been given the choice to either create - or destroy.

Merlin had been given the privilege of doing both. Although, deep down, he knew his trail of carnage was far more prominent than his history of creation.

He stood at the edge of the grassy bank, staring into the sparkling black water - admiring, for the last time, the moon's scattered light. As a faint Zephyr teased through his hair, his fingers tightened over an invisible hilt.

 _His King had arrived._

The sound of flapping wings and soft rustling grass told him that his invitation had been received and accepted. So overdue was this call. How he had _longed_ to see him up close. He spun around with apathy written on his face.

His eyes roamed the skeletal branches of the trees around them, where thousands of ravens chose to perch upon in silence. Six black mambas encircled the man - no, _Beast -_ before him, while another six Rottweilers stood on guard in front.

An impressive sight.

"Damien Thorn, President of the United States of America and-" his lips twitched in amusement before he shifted into his British Accent, "-Acting Prime Minister of Great Britain, at your service," claimed the beguiler.

 _No, he's the real thing_ , Merlin corrected himself. _He just isn't as you would expect him to be_.

"You said you wanted to see me?" his guest queried, betraying no emotion. If he indeed remembered Merlin and recognized him, he didn't show it. Even from where he stood, Merlin could see the red glinting off the corners of Damien's dark blue irises.

 _Arthur's_ dark blue irises. Once upon a time, a bright azure.

 _Was there truly no hope for Arthur?_

"Indeed, I do." He arched an eyebrow. "Frankly, I've been wanting to see you for the past two thousand years. For a moment there I thought you wouldn't come," Merlin said, offhandedly, keeping a steady grip on the blade he had enchanted to be the colour of air. His palms were dreadfully sweaty.

He really didn't want to do this.

" _Arthur will rise again when Albion's need is greatest."_

His eyes drank in the sight of his beloved king, brought back to life after all these centuries. It was like gulping down a glass of crystal water on a broiling summer day - that was laced with hemlock, the reality of it suffocating him. Kilgharrah's prophecy was indeed accurate. Except… _Except it was twisted beyond comprehension._

 _Arthur_ was _Albion's cause for its need._

He was destined to bring about the Apocalypse.

And it had taken Merlin _this_ long to come to that realization.

"Arthur," he muttered, hoarsely.

Arthur flinched visibly. "Don't call me that." If his eyes were already dark, then they darkened even further. "I'm no longer that person. I don't deserve to be identified as him."

"But you _are_ him. You _are_ Arthur Pendragon. King of Camelot. Founder of the Round Table. Gwen's husband." Merlin pursed his lips. " _Destined to unite Albion."_

 _Destined to bring back magic to the land with me._

"My best friend who I would've willingly died for anytime."

Arthur held up a hand. "I know. I know _everything._ But that cannot change what is the present."

Then Merlin felt the shift. Something so sudden and yet so subtle he wondered if he'd dreamt it up. Like a current in the air somehow chilled, crackling with potent devilcraft like electricity, and for the first time ever in the past few centuries…

Merlin felt scared.

"Oh, but I already have, haven't I? United Albion in their fight _against me._ " The Prime Minister tilted his head sideways. "By all rights, I've already fulfilled _both_ segments of my destiny.

"Aren't you proud, _Emrys_? Magic reigns freely once more, running rampant across the globe. After all, sorcery is the tool of the Devil - Christianity's next biggest adversary. Without it, the world wouldn't be what it is right now," mused Arthur, an arctic smile that should've belonged on Morgana's face adorning his own visage.

Ice shot through Merlin's veins. Never. Never in _hell_ would he have expected Arthur to address him by that title.

"It wasn't supposed to _be this way_ ," he hissed, through gritted teeth.

To think, that _Arthur Pendragon_ of all people, would utilize magic in such a tainted way. He, who had shunned magic for the entirety of his life until his final moments before death. He, who Merlin had worked his hardest to show the _good_ of magic.

Before being reborn as the son of Satan.

His eyes flicked to the western sky, where he could discern faint silvery lines heralding the break of dawn.

The world _was_ truly ending.

"Do you think I _wanted_ this? Don't you think I would've taken any other alternative had it been there?" Arthur - _Damien_ , he wasn't sure anymore - growled back. "No matter what we'd like to think, I can't help being the son of Satan as much as you can't help being the most powerful warlock to ever exist. Like how you were required to take up the mantle of Emrys, I was destined to take up the role of the Antichrist.

"I'm sure _you_ of all people would understand how much Destiny can't be defied." He laughed bitterly.

"There is _no_ other way."

Merlin's heart clenched even further, those five simple words piercing through him like a million poison darts. Nausea hit him like a pile of bricks as he vividly remembered another person saying those exact words to him. A dear friend he had made the mistake of pushing away. Until her heart festered in bitterness and hatred.

Until she became his worst enemy.

"You're no different from Morgana now," Merlin breathed.

"I won't deny that. But neither are you," Arthur shot back, coolly, unperturbed by the accusation. "It's quite funny how people these days perceive a Warlock as synonymous with the Devil."

He... he couldn't deny that either, because day in and day out, he found himself making too many choices that destroyed other people's lives as well. Found himself becoming less and less remorseful about his kills.

And that was where the similarities ended.

Unlike Morgana, he knew when the game was over. Which was precisely why he'd already made his checkmate by meeting Arthur today.

But Arthur didn't know that.

"This is all my fault. I should've found you sooner," Merlin's whispered, his throat thickening. "I failed you all over again."

The resurrected king watched him calmly.

Merlin felt a harrowing sense of déjà vu wash through him as he shook his head. " _But this has to end."_

"All seven Daggers of Megiddo have been lost forever. There's not much you can do now, really," Arthur said, blandly.

"That's where you're wrong. This eidolon of sin you have created - it _will_ shatter."

Merlin's eyes burned a furious gold, and in a flash of silver, all said daggers materialized from the air and surged to where Arthur's heart was.

And… _now!_

The crows around them took flight in unison to form an ebony shield before their master. Several of them dropped dead as the daggers embedded themselves into their bodies. The black dogs dashed forth, with the intent of sinking their teeth into his flesh, while venomous serpents followed suit at a terrifying pace.

But Merlin was even faster.

He spiraled out of the way, leaping, turning, running, and dispatching these animals with a simple flick of his eyes. It was exhilarating - the struggle. There was only one thing left to do, and in truth, it would be so easy.

He was slaying the Antichrist. Not Arthur.

 _The Antichrist. Not Arthur. The Antichrist. Not Arthur. The Antichrist. Not Arthur. The-_

"Once and Future King," uttered The Beast, matter-of-factly.

His focus wavered, and a wave of dark energy slammed into him, stunning him a few steps back.

 _No. He would not fall for such mind games._

He leaped to the left, before another surge of devilry could blast him back, freezing The Beast in its spot for the next few seconds-

-and lunged, thrusting the immortal blade between its ribs.

Ember-like tendrils spread across the sword - finally uncovering the true form of its make, turning the enchantment null. A dark red bloomed across Damien's shirt.

 _Nothing_ could describe the kind of horror Merlin was feeling then.

"You actually... did it," the Antichrist choked out, as blood dribbled down his chin.

"I know a lost cause when I see one," he replied, flatly.

The Beast smirked. But it was an expression free of malice. Only amusement and…

Relief?

"So _I'm_ a lost cause then, _Mer_ lin?"

Oh gods. _How dare he..._

His face contorted in pain as agony ripped through his being. "No… _never._ You were my purpose. Always have been."

Tears burnt at the back of his eyes. "But the risk of your continued existence is simply too great."

 _And so is mine._

But thank whatever deity out there that it was almost over - this whole nightmare.

Arthur's hand clawed at the area where the blade protruded from his chest, casting blurry eyes at it. "Ahh… dear old Excalibur… What a fool I am to have… forgotten about her." He coughed severely. "The legendary sword pulled out of the stone… Able to slay those who cannot die... Made godlike... from being burnished in the Dragon's breath…"

Merlin refused to be surprised anymore by Arthur's vast knowledge of things he couldn't have possibly known. He was, after all, the Antichrist - granted divine powers that rivalled even his own.

It was just so out of place.

"How oddly befitting... to have my incompetent manservant kill me... with my own sword."

Merlin retracted the blade before Arthur could make anymore smartass remarks, leaving him to slump to the ground.

"Thank you again... old friend," he whispered, as the light faded from his eyes. _Free_ , they spoke. _Finally free from this madness._

He nodded curtly, choking down the sobs that threatened to surface. "Till we meet again."

Be it in Heaven or Avalon. Or even Hell.

Merlin closed his eyes, tilting his head backwards as he took in a deep breath - embracing the death before him as the final fragment of his soul broke off.

Just like Excalibur, it would lie deep in the ocean, dead and cast away.

 _Requiem aeternam dona eis…_

 _[Grant them eternal rest]_

" _In sebbe gerrest_ _(Rest in peace)_ ," he murmured, softly. This time, he directed it not just to Arthur, but to everyone else who had perished in this grand design - from the dawn of time to this very moment. From the most evil to the most benevolent.

And to those who would perish on _this_ very day.

 _Dies irae... dies illa..._

 _[Day of wrath, day of anger]_

The day when the sun rose in the west and set in the east. The day when stars would fall from Heaven and the earth would be drowned in a sea of flame.

 _Solvet saeclum in favilla..._

 _[Will dissolve the world in ashes]_

He glanced at the bloodied blade in his palm, and wondered, if it was wise to stab himself there and then. At least then, he would be able to save himself from experiencing the dire catastrophe promised to come.

 _Quantus tremor est futurus…_

 _[How much tremor there will be...]_

 _No._ He would not be a coward. He would be there when the rest of humanity was led to further ruin.

He flung the ethereal sword into the lake without hesitation.

Merlin essentially didn't know what to believe in anymore, and neither did he care. Whether there was a One True God that lorded over them, or if the Old Religion of Magic had been a lie all this long…

He would face his sentence with his head held up high.

 _Quando Judex est venturus… Cuncta stricte discussurus!_

 _[When the Judge descends from heaven... to sentence all things strictly!]_

The earth trembled beneath him; brimstone rained from the empyrean.

And the world dissolved in ashes.

 **A/N: Thank you for reading! Reviews will be nice.**


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